This invention relates to pontoon boat structures and particularly to structures that strengthen the pontoons, increase the deck area of the boat, and make it easier to steer the boat in the water and to support it without damage when it is out of the water.
Most commercial pontoon boats are based on two parallel cylindrical floats made of sheet metal bent to form round tubes that are closed and sealed watertight at each end and along each seam. While round floats provide the greatest buoyancy per square foot of the sheet metal used to make them, they have several important disadvantages. For one thing the deck bridged across the pontoons is joined to them in such limited areas that the structure cannot withstand much wave action. For another, the hydrodynamic inefficiency of such pontoons requires a considerable amount of power to force the boat forward at anything above a sedate speed, and the boats are not easy to steer. In addition, when hauled out of water, the round sheet metal can be easily bent and torn and is difficult to repair. This leads to problems in beaching boats with round pontoons and in towing them on a trailer.
Efforts have been made to improve pontoon boats by various constructions. In U.S. Pat. No. 2,775,218, to Kapusnyk shows a boat in which tubular aluminum pontoons are connected together by arms that pivot at each end to allow the whole structure to be folded up. The pontoons have elliptical cross-sections, and each pontoon has two small, rounded fins spaced along the bottom.
U.S. Pat. No. 3,839,979 to Wassell shows another collapsible pontoon boat structure.
U.S. Pat. No. 4,223,620 to Dudouyt shows a rigid catamaran structure having floats, each consisting of molded shells joined together along a central seam and at least partly filled with rigid foam.
U.S. Pat. No. 4,582,012 to Montgomery shows a boat that has two inflatable pontoons,
U.S. Pat. No. 4,730,571 to Hedlund et al. shows a pontoon boat having a parallel linkage connected to it and providing pivotal connections between the pontoons and a central passenger seat.